1. Field of the Invention
The present invention relates generally to a dual mode satellite/cellular portable phone and, in particular, to an antenna system for a dual mode satellite/cellular portable phone.
2. Description of Related Art
Portable cellular phones are well known and have been utilized for the past several years. Such cellular phones typically transmit and receive signals at a frequency of approximately 800-950 Megahertz by means of an antenna designed for such purpose. Recently, however, it has become desirable for a second mode of communication, (e.g., satellite) to be employed in areas where cellular towers or stations are not available. Satellite communication occurs at frequencies much higher than for cellular communication (typically 1.0-3.0 Gigahertz) and likewise requires an antenna specifically designed for such communication. It will be understood that there are certain differences between an antenna utilized for cellular communication versus one utilized for satellite communication. One example is that the cellular antenna will preferably be linearly polarized so as to function as a monopole while the satellite antenna is circularly polarized in order to provide hemispherical coverage. A further distinction is that communication in the satellite mode involves a directional component (where link margin is increased when the satellite antenna is pointed toward the satellite), whereas communication in the cellular mode does not.
Because at least some of the characteristics desirable for the cellular and satellite antennas are inconsistent, one approach that has been taken is the antenna system shown and disclosed in a patent application entitled "Antenna System For Dual Mode Satellite/Cellular Portable Phone," Ser. No. 08/586,433, also filed by the assignee of the present invention. As seen therein, separate antennas were provided with a portable phone for cellular and satellite communication. While the antenna system disclosed by this patent application is adequate for its intended purpose, it will be noted that an antenna system having only a single antenna which can be utilized for both cellular and satellite modes of communication would be preferred from the standpoints of cost and aesthetics.
In light of the foregoing, a primary objective of the present invention is to provide an antenna system for a portable phone which enables the transmission and receipt of signals in both cellular and satellite modes of communication.
Another object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which includes only a single antenna for transmitting and receiving signals in cellular and satellite modes of communication.
A further object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which is mounted so as to enable better link margin with respect to an applicable satellite.
Yet another object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which minimizes the need for manipulation by the user thereof.
Still another object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which is aesthetically pleasing to the user thereof.
Another object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which minimizes the overall impact on size of the portable phone.
A still further object of the present invention is to provide an antenna system for a dual mode satellite/cellular portable phone which permits the use of separate frequency sub-bands for transmitting and receiving signals within the satellite and cellular modes of communication.
These objects and other features of the present invention will become more readily apparent upon reference to the following description when taken in conjunction with following drawing.